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A boutonnière deformity consists of flexion of the proximal interphalangeal (PIP) joint accompanied by hyperextension of the distal interphalangeal (DIP) joint (see see Figure: Boutonnière and swan-neck deformities.).
This deformity can result from tendon laceration, dislocation, fracture, osteoarthritis, or RA. Classically, the deformity is caused by disruption of the central slip attachment of the extensor tendon to the base of the middle phalanx, allowing the proximal phalanx to protrude (“buttonhole”) between the lateral bands of the extensor tendon. Initial treatment consists of splinting, but it must occur before scarring and fixed deformities develop. Surgical reconstruction often cannot restore normal motion but may decrease the deformity and improve hand function.
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